Quick Tour of Temper

Temper is a programming language and toolchain for making libraries that can be used natively from any other language.

Temper compiles to idiomatic types and functions for each target language: currently Python, JavaScript, C#, Java, and Lua, with plans for many more. Whether you're an open-source developer or work in an enterprise, Temper can multiply the reach and effect of your work. "Why a new programming language?" explains what Temper lets you do that existing languages don't.

Get started, or see examples below for a quick tour.

Examples

Translate

Temper lets you define rich data types and logic that translate to all supported backend languages. Usage is idiomatic in each language.

export class Person(
  public birthDate: Date,
) {
  public ageAt(date: Date): Int {
    // Or support other definitions of age.
    date.yearsSince(birthDate)
  }
}

Use from:

C#JavaJS / TSLuaPython

using Snippets.Person;

var person = new Person(new Date(1987, 6, 5));
var age = person.AgeAt(new Date(2023, 2, 1));
Console.WriteLine($"Age: {age}");

import snippets.person.*;

class Use {
    public static void main(String[] args) {
        var person = new Person(new Date(1987, 6, 5));
        var age = person.ageAt(new Date(2023, 2, 1));
        System.out.printf("Age: %s\n", age);
    }
}

import { Date, Person } from "snippets/person.js";

let person = new Person(new Date(1987, 6, 5));
let age = person.ageAt(new Date(2023, 2, 1));
console.log(`Age: ${age}`);

local p = require("snippets.person")

local person = p.Person(p.Date(1987, 6, 5));
local age = person:ageAt(p.Date(2023, 2, 1));
print("Age: " .. math.floor(age));

from snippets.person import Date, Person

person = Person(Date(1987, 6, 5))
age = person.age_at(Date(2023, 2, 1))
print(f"Age: {age}")

Dispatch

Use interfaces for abstraction. And use familiar syntax.

export interface Shape {
  public perimeter(): Float64;
}

export class Rectangle(
  public width: Float64,
  public height: Float64,
) extends Shape {
  public perimeter(): Float64 { 2.0 * (width + height) }
}

let tau = 2.0 * Float64.pi;

export class Circle(
  public radius: Float64,
) extends Shape {
  public perimeter(): Float64 { tau * radius }
}

When

Or match on types instead of using virtual dispatch.

export let area(shape: Shape): Float64 {
  when (shape) {
    is Rectangle -> shape.width * shape.height;
    is Circle -> do {
      let { radius } = shape;
      0.5 * tau * radius * radius
    }
    else -> NaN; // needed until exhaustiveness checks
  }
}

Test

Test your code across languages. Temper test integrates with well-known frameworks such as JUnit, Mocha, and Pytest. You can test your libraries in Temper to build confidence in its correctness and also build confidence in each translation's fidelity.

test("age") {
  let person = new Person(new Date(1987, 6, 5));
  let age = person.ageAt(new Date(2023, 2, 1));
  // You can give a custom failure message callback.
  assert(age == 35) { "Bad age: ${age.toString()}" }
  // Or just use automatic messaging.
  // Reports "expected age == (36) not (35)"
  assert(age == 36);
}

Document

Embed your Temper code inside of Markdown. Collaborate with others on lightweight standards documents that include a reference implementation. Translate the implementation to many programming languages.

## Circle

Tau (τ) is a full turn in radians, rather than the half turn of pi (π).

    let τ = 2.0 * Float64.pi;

    export class Circle(
      public radius: Float64,
    ) {

Using `τ` rather than `π` simplifies some calculations and complicates
others.

      public perimeter(): Float64 { τ * radius }
    }

Develop

We've implemented an initial Temper language server and an extension for Visual Studio Code. Great tooling helps Temper users discover language features and iterate quickly, so we'll continue to prioritize it.

Next steps

Excited about Temper?

• Get started
• or read the reference documentation.

Problems, Questions, Discussion?

• Questions, the [temper] tag is a great place to ask.
• Ideas, or just want to chat? The Temper Language Discord is a great place to share your thoughts on Temper or talk about what you've done with it.
• If you have a problem or feature request, check the issue tracker.